Tyco MR601TEx Product information

Brand: Tyco

Model: MR601TEx

Type: Product information

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MR601TEx INTRINSICALLY SAFE ENHANCED OPTICAL SMOKE DETECTOR

PRODUCT APPLICATION AND DESIGN INFORMATION

1. INTRODUCTION

The MR601TEx Intrinsically Safe High Performance Optical

Smoke Detector forms part of the M600Ex series of plug in

detectors for ceiling mounting. The detector plugs into the

5BEx 5” Universal IS Base and is intended for two-wire

operation on the majority of the control equipment currently

manufactured by the company. The Intrinsically Safe High

Performance Optical detector is available in one sensitivity

setting only.

2. INTRINSIC SAFETY

The detectors are for use in potentially explosive gas and dust

atmospheres (zone 0 gas, zone 20 dust).

The detectors are designed to comply with EN/IEC 60079-

0:2006, EN/IEC 60079-11:2007 and EN/IEC61241-11:2006 for

Intrinsically Safe apparatus. They are certified:

ATEX code:

II 1 GD

Certificate: BAS01ATEX1134X

Gas/Dust code: Ex ia IIC T5

Ex iaD 20 T100°C

IECEx Certificate: IECEx BAS 07.0056X

These detectors are designed and manufactured to protect

against other hazards as defined in paragraph 1.2.7 of Annex II

of the ATEX Directive 94/9/EC.

2.1 DETECTOR USE

It is recommended that the detector is used in conjunction with

a suitable isolator or shunt diode safety barrier in a certified

Intrinsically Safe system, ie, System 620.

2.2 SPECIAL CONDITIONS OF SAFE USE

The apparatus has a plastic enclosure which constitutes a

potential electrostatic hazard. The enclosure must be cleaned

only with a damp cloth.

3. OPERATING PRINCIPLE

The MR601TEx operates by sensing the optical scatter from

smoke particles generated in a fire. While the optical scatter

detector can give good detection performance for the majority

of fires, some fast burning fires produce little visible smoke and

some produce very black smoke, neither of which are easily

detected by the optical scatter detector. (Such fires are

represented in EN54-7 by Polyurethane and Heptane type fires

respectively). These fires do, however, produce high heat

outputs with an associated rise in air temperature.

The detector has been designed to offer improved detection of

such fires, by detecting the rapid rate-of-rise of air temperature

and under these conditions, increasing the smoke detection

sensitivity. This gives an earlier detection of such fires and a

broader detection capability than a standard detector.

The MR601TEx detector has two sensing systems as follows:

• An optical chamber with associated electronics

to measure the presence of smoke by light

scatter.

• A thermistor with its associated electronics to

detect the presence of hot air draughts or high

temperatures.

Fig. 1 Optical System Schematic

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SMOKE

PATH

SAMPLING

VOLUME

FINS

Fig. 2 Measuring Chamber Showing Smoke Flow Path

3.1 OPTICAL SYSTEM

The MR601TEx detects visible particles produced in fires

by using the light scattering properties of the particles. The

detector uses the optical arrangement shown

diagrammatically in Fig. 1.

The optical system consists of an infra-red emitter and

receiver, with a lens in front of each, so arranged that their

optical axes cross in the sampling volume. The emitter,

with its lens, produces a narrow beam of light which is

prevented from reaching the receiver by the baffles. When

smoke is present in the sampling volume a proportion of the

light is scattered, some of which reaches the receiver. For a

given type of smoke, the light reaching the photodetector is

proportional to the smoke density. The amplified output

from the sensor can be used to activate an alarm circuit at a

predetermined threshold.

FINS

REFERENCE

SENSING

Fig. 3 Thermal Measuring System

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STATUS

LED

EMITTER

PHOTO

DIODE

SENSOR

AMPLIFIER

GAIN

TIMER/

OSCILLATOR

SYNCHRONOUS

DETECTOR

COMPARATOR

REF

SENSING

THERMISTOR

REFERENCE

THERMISTOR

COMPARATOR

THRESHOLD

LED

OUTPUT

SWITCH

COUNTER

LINE A IN

LINE A OUT

LINE B IN/OUT

BRIDGE

BASE

REMOTE LED

Fig. 4 Block Schematic of Detector

3.2 FEATURES OF MEASURING CHAMBER

The MR601TEx uses vertical chevrons to exclude ambient

light.

Smoke incident on the detector is channelled into the

detector by the outer cover fins (Fig. 2) and passes through

the vertical chevrons. The smoke is deflected into the

optical chamber and through the sampling volume before

passing out the other side of the detector.

The emitter (Fig. 1) is a GaAlAs solid state type operating

in the near infra-red (880nm peak), while the detector is a

matched silicon photodiode. These devices, together with

their associated lenses, are held in place by the chamber

mouldings. The design of the optical system is such that the

presence of small insects such as thrips, should not cause

false alarms.

3.3 THERMAL MEASURING SYSTEM

Refer to Fig. 3.

This is designed to detect the presence of horizontally

moving hot air draughts moving across the ceiling which

occur in a fast burning fire.

The measuring system consists of two fast responding

negative temperature thermistors. A sensing thermistor is

located above the labyrinth under the cover in the airstream

and will detect any sudden changes in the air temperature or

draughts of hot air moving across the ceiling. The second

thermistor is located out of the airflow within the smoke

labyrinth and has a longer time constant and is used as a

temperature reference to compare the sensing thermistor

against. At a given temperature differential between the

two thermistors, the comparator will switch and increase the

gain of the amplifier, thereby increasing the sensitivity of

the sensor. Fins located on the top of the labyrinth are

designed to increase air turbulence and the efficiency of the

sensing thermistor.

3.4 CIRCUIT OPERATIONS

A simplified block schematic of the detector is given in

Fig. 4.

The emitter is subjected to a pulse stream only every 10s in

order to reduce the quiescent current. The pulse signal

received by the photodiode is fed to a high-gain

amplifier. If smoke is present, the pulse signal received

varies in proportion to the smoke density.

The amplifier output is fed via an integrator, the output of

which is compared to a preset threshold

level. Sophisticated synchronous detection techniques are

used to reduce the effects of noise and spurious transients.

The gain of the front end amplifier is controlled by the

thermistor bridge circuit. When the temperature differential

between the two thermistors exceeds a certain value, the

amplifier gain increases. Under these conditions the High

Performance Optical detector is more sensitive to the

presence of smoke and is said to be in ‘Enhanced Mode’.

When the detector is in the ‘Enhanced Mode’, the detector

will only alarm if a smoke signal is present. The presence

of rising temperature alone cannot cause an alarm.

If the signal amplitude exceeds a threshold level, then the

emitter samples the smoke every two seconds. The sample

period remains at two seconds if the signal is above the

threshold. When the counter has counted three consecutive

pulses above the threshold, the output stage is latched into

the alarm condition. If however, the amplitude of the

second or third pulse is below the threshold, then the pulse

period reverts to 10 seconds and the counter resets. The

switching of the output stage lights the alarm LED and

provides drive for the remote LED indicator.

The critical front end of the circuit is run off a 12V regulator

to make it independent of supply voltage.

The detector is polarity conscious.

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Fig. 5 Overall Dimensions of MR601TEx

109

3.5 WIRING

Loop cabling is connected to base terminals as follows:

L-VE

L1 +VE IN

L2 +VE OUT

R Remote LED Drive

4. MECHANICAL CONSTRUCTION

The major components of the detector are:

• Body Assembly

• Printed Circuit

• Optical Chamber

• Optical Chamber Cover

• Thermistor

• Light Pipe

• Outer Cover

4.1 ASSEMBLY

The body assembly consists of a plastic moulding which has

four embedded detector contacts which align with contacts

in the 5BEx base. The moulding incorporates securing

features to retain the detector in the base.

The PCB is soldered to the body contacts. These contacts

act as a mechanical fixture during assembly and provide

electrical contact between the contacts and the PCB. The

PCB is then potted.

The chamber cover is clipped to the body over the optical

chamber ensuring the thermistor protrudes through the

cover. The light pipe is slotted into the chamber

cover. Finally, the outer cover is clipped to the body.

4.2 TEST AND FINAL ASSEMBLY

The detectors are fully functionally tested and their

sensitivities set in a smoke tunnel to ensure correct

calibration. The sealing ring and labels are then fitted to

complete detector assembly.

5. TECHNICAL SPECIFICATION

5.1 MECHANICAL

Dimensions

The dimensions of the MR601TEx detector are shown in

Fig. 5.

Materials

Body and cover: FR110 ‘BAYBLEND’

Fire Resistant

Fig. 6 MR601TEx Enhanced Optical Smoke Detector

with 5BEx 5” Base

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0 2 4 6 8 10 12 14 16 18

Detector Voltage (V)

Detecor Current [mA]

Fig. 7 Alarm Load Presented to the Controller

Weight

Detector: 0.128kg

Detector + base: 0.174kg

5.2 ENVIRONMENTAL

Operating Temperature: -20

C to +70

(please see note below).

Storage Temperature: -25

C to +80

Note:

1) The operating temperatures quoted exceed

the ATEX Certification limits.

2) Operation below 0

C is not recommended

unless steps are taken to eliminate

condensation and hence ice formation on the

detector.

Relative Humidity: 95% non-condensing

Shock: )

Vibration: )

Impact: ) To EN54-7

Corrosion: )

5.3 ELECTROMAGNETIC COMPATIBILITY

The detector complies with the following:

Product family standard EN50130-4 in respect of

Conducted Disturbances, Radiated Immunity,

Electrostatic Discharge, Fast Transients and Slow High

Energy

EN 61000-6-3 for Emissions

5.4 ELECTRICAL CHARACTERISTICS

The alarm load presented to the controller is shown in Fig. 7.

The following characteristics shown in Table 1 are taken at

C with a supply voltage of 20V unless otherwise

specified.

Intrinsic Safety Rating:

Maximum Voltage for safety (U

): 28V

Maximum Current for Safety (I

): 93mA

Maximum Power Input (P

): 650mW

Equivalent Inductance (L

): 0

Equivalent Capacitance (C

): 0

5.5 PERFORMANCE CHARACTERISTICS

The fundamental parameter used to define the sensitivity of

an optical smoke detector is the level of smoke which will

just produce an alarm under ‘ideal’ conditions. This

parameter, known as the response threshold value, is

normally measured in a smoke tunnel and is defined in

terms of the obscuration produced by the smoke over a one

metre path. The response threshold value is normally given

in dB/m, (or % per m).

Characteristics Min. Typ. Max. Unit

Operating Voltage (d.c.) 16 20 28 V

Average Quiescent Current 90 110 μA

Switch-on-Surge 130 μA

Stabilisation Time 60 sec

Alarm Current See Fig. 6 mA

Holding Voltage 5 V

Holding Current 1 mA

Reset Time 2 5 sec

Remote LED Drive Remote LED via 3.4k

Table. 1 Electrical Characteristics

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Interpretation of response threshold value is somewhat

complicated by the fact that the measurement is given in

terms of obscuration, whereas the detector works by

scattering from the smoke particles. The response threshold

(m) value will therefore, depend on the colour of the

smoke. Black smokes give less scattering than light smokes

for given values of obscuration as shown in Fig. 8.

Sensitivities are invariably specified for ‘grey’ smokes as

produced by typical smouldering fires. Values for the

MR601TEx are given below.

5.5.1 RESPONSE TO RATE OF CHANGE

OF TEMPERATURE

The detector will not be enhanced by slow rates of change of

temperature, or by cold air draughts moving across the

ceiling creating negative rates of change of

temperature. The detector is designed to detect sudden

horizontal draughts of hot air produced by fast burning

fires. The enhancement switching point has been set to

allow the detection of TF1 type fires.

Normal response threshold = 0.19 dB/m, 2.7%/m typical.

Enhanced mode threshold = 0.08 dB/m, 1.1%/m typical.

5.6 RESPONSE TO FIRE TESTS

The response of an optical scatter detector to a fire will

depend to a large extent on the colour of the smoke produced

in the fire. However, other factors such as the detector

smoke entry characteristics, the development of the fire and

the thermal lift produced by the fire are important. In order

to evaluate the response under realistic conditions, detectors

are subjected to test fires which cover a range of fire

types. These tests are defined in EN54 Pt 7. The

MR601TEx passes the following Fire Tests:

Fig. 8 Response Threshold vs Smoke Colour

Note: TF2 to TF5 are mandatory test fires required to

meet EN54 Pt 7.

The MR601TEx is designed to respond to the mandatory

tests TF2 to TF5 as required by BS5445 Pt 7. The

MR601TEx gives an earlier response to TF5 fires than the

MR601 due to its thermal circuit detecting the heat

generated by this test of fire and the MR601TEx being

‘enhanced’. For the same reason the MR601TEx will

detect test fire TF1 (open wood cellulosic flaming fire)

which is not normally detected by optical smoke detectors -

demonstrating the detectors broader detection capability.

The MR601TEx does not respond to TF6 liquid

(methylated spirit) which although having a rapidly rising

temperature, does not generate any optical scattering. This

shows that the High Performance Optical detector will not

respond to hot air draughts without the presence of smoke.

6. INSTALLATION

RECOMMENDATIONS

It is not recommended that the MR601TEx be installed in

areas where it is likely to be regularly enhanced, since in

this condition the detector is extra sensitive and there is a

possibility of unwanted alarms from low ambient smoke

levels.

The MR601TEx is designed to become enhanced by

detecting a rapid temperature rise (>10°C) in air moving

horizontally across the ceiling. Siting sensors in positions

where air is being blown through the detector should

therefore, be particularly avoided, eg, close to ceiling ducts

or ceiling mounted industrial heaters; or areas of forced

ventilation, such as ducts and under floor voids of computer

suites.

Also, not recommended are areas open to the outdoors, such

as cargo handling bays, or areas where the detector may

become contaminated.

The MR601TEx is not recommended for use in applications

where a heater jacket is required.

The MR601TEx is primarily aimed at benign

environments.

TF1 open cellulosic (wood-flaming)

TF2 smouldering pyrolysis

TF3 glowing smouldering (cotton)

TF4 open plastics (polyurethane foam)

TF5 liquid (n-heptane)

Table 2: Response to Fire Tests

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7. CPD INFORMATION

8. DETECTOR IDENTIFICATION

The detector is identified by the logo label, as shown in

Fig. 9.

0832

Tyco Safety Products

Dunhams Lane

Letchworth SG6 1BE

0832-CPD-0248

MR601TEx

Application & Design 01B-04-D12

Installation Instructions 01B-04-I3

Service Instructions 01B-04-S2

EN 54-7: 2000 + A1: 2002

Conventional Intrinsically Safe high

performance photoelectric smoke detector

with heat enhancement for use in fire

detection and alarm systems in buildings

tyco

Fig. 9 Detector identification

GREEN

9. ORDERING INFORMATION

MR601TEx Intrinsically Safe

Enhanced Optical Smoke Detector: 516.054.011.Y

5BEx 5” Universal IS Base: 517.050.023

JM/jm

May 2010

Tyco MR601TEx Product information

Tyco MR601TEx Product information

Tyco MR601TEx Product information

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